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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Diagnoses of fipronil resistance in Brazilian cattle ticks (Rhipicephalus (Boophilus) microplus) using in vitro larval bioassays

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Author(s):
Castro-Janer, E. [1, 2] ; Martins, J. R. [3] ; Mendes, M. C. [4] ; Namindome, A. [1] ; Klafke, G. M. [1] ; Schumaker, T. T. S. [1]
Total Authors: 6
Affiliation:
[1] Univ Sao Paulo, Inst Ciencias Biomed, Dept Parasitol, BR-05508 Sao Paulo - Brazil
[2] UDELAR, Fac Vet, Dept Parasitol, Montevideo - Uruguay
[3] FEPAGRO, Inst Pesquisas Vet Desiderio Finamor, Rio Grande Do Sul - Brazil
[4] Ctr Pesquisa & Desenvolvimento Saude Anim, Inst Biol Sao Paulo, Setor Parasitol, Sao Paulo - Brazil
Total Affiliations: 4
Document type: Journal article
Source: Veterinary Parasitology; v. 173, n. 3-4, p. 300-306, OCT 29 2010.
Web of Science Citations: 52
Abstract

Fipronil is a phenylpyrazolic insecticide that is widely used in agriculture and has been recently used to control the cattle tick, Rhipicephalus (Boophilus) microplus. Because of the serious problems associated with resistance to the available acaricides, this product has been used as an important alternative to control acaricide-resistant ticks. The objective of this work was to analyse the fipronil sensitivity of ticks that were collected from farms with a history of fipronil use by larval bioassays. A total of 11 Brazilian tick populations were studied: one population from Rio Grande do Sul, one population from Mato Grosso do Sul and nine populations from Sao Paulo. To validate the assays, susceptible reference strains, POA (Porto Alegre, Brazil) and Mozo (Dilave, Uruguay), and ticks from six different farms that never used fipronil were tested. The resistance of various tick populations to technical grade fipronil (95.3%) was primarily evaluated using the larvae immersion test (LIT) and the larval packet test (LPT), when a sufficient number of larvae was collected. Using the LIT, the resistance ratios (RR(50)) of the tick populations from Rio Grande do Sul and Mato Grosso do Sul were 14.9 and 2.6, respectively, and the populations derived from Sao Paulo had RR(50)s ranging from 2.5 to 6.9. Four populations were evaluated with the LPT, and two populations displayed lower RR(50), while other populations displayed higher RR(50) than those determined by the LIT. This article reports the first cases of fipronil resistance in Brazil and highlights the LIT as a more sensitive technique for the evaluation of fipronil resistance in R. (B) microplus ticks. We suggest the use of the LIT as an evaluation tool for monitoring fipronil resistance in the control programmes of R. (B) microplus. (C) 2010 Elsevier B.V. All rights reserved. (AU)